[tex]A=2^{2n}*25^{n}*5-4^{n}*5^{2n} \\ \\ A=2^{2n}*(5^{2})^{n}*5-(2^{2})^{n}*5^{2n} \\ \\ A=2^{2n}*5^{2n}*5-2^{2n}*5^{2n} \\ \\
A=2^{2n}*5^{2n+1}-2^{2n}*5^{2n} \\ \\
A=2^{2n}*5^{2n}(5^{1}-1) \\ \\
A=[(2^{n})^{2}*(5^{n})^{2}]*2^{2}[/tex]
Este un produs de patrate perfecte , deci e un patrat perfect.